Process and catalyst for the hydroconversion of a heavy hydrocarbon feedstock

ABSTRACT

A method of hydroprocessing a heavy hydrocarbon feedstock using a hydroprocessing catalyst having specific properties making it effective in the hydroconversion of at least a portion of the heavy hydrocarbon feedstock to lighter hydrocarbons. The hydroprocessing catalyst comprises a Group VIB metal component (e.g., Cr, Mo, and W), a Group VIII metal component (e.g., Ni and Co) and, optionally, a potassium metal component that are supported on a support material comprising alumina. The alumina has novel physical properties that, in combination with the catalytic components, provide for the hydroprocessing catalyst. The hydroprocessing catalyst is particularly effective in the conversion of the heavy hydrocarbon feedstock. The alumina is characterized as having a high pore volume and a high surface area with a large proportion of the pore volume being present in the pores within a narrow pore diameter distribution about a narrowly defined range of median pore diameters. The support material preferably does not contain more than a small concentration of silica. The alumina component is preferably made by a specific method that provides for an alumina having the specific physical properties required for the hydroprocessing catalyst.

This application is a divisional application of prior application Ser.No. 10/941,462, filed Sep. 15, 2004 now U.S. Pat. No. 7,790,652, nowallowed, which claims the benefit of U.S. Provisional Application No.60/503,733, filed Sep. 17, 2003.

BACKGROUND OF THE INVENTION

This invention relates to a process and a catalyst composition used inthe process for the hydroprocessing of a heavy hydrocarbon feedstock.Another aspect of the invention includes a catalyst support materialthat can be used as a component of the hydroprocessing catalystcomposition to impart certain physical properties, which make thehydroprocessing catalyst composition particularly useful in thehydroprocessing of a heavy hydrocarbon feedstock.

The catalytic hydrotreatment of hydrocarbon feedstock in order to removetherefrom impurities such as sulfur, nitrogen, and metal compounds is acommonly used process to improve or upgrade such hydrocarbon feedstock.In a typical hydrotreating process, the hydrocarbon feedstock iscontacted in the presence of hydrogen with a hydrotreating catalystunder process conditions that suitably provide for a treated hydrocarbonproduct. The hydrotreating catalysts used in these processes generallyare composed of an active phase that can include a component from theGroup VIB metals and a component from the Group VIII metals supported ona porous, refractory inorganic oxide material.

The hydrotreatment of heavy hydrocarbon feedstock is particularlydifficult; because, such feeds tend to have high concentrations ofcontaminating sulfur and metal compounds and may require the use of moresevere process conditions than those needed to treat lighter hydrocarbonfeedstock. Also, the heavy hydrocarbon feedstock can contain a heavyboiling fraction which a portion thereof is to be converted into lighterand more valuable components. As a result of the particularcharacteristics of a heavy hydrocarbon feedstock, the hydroprocessing ofsuch a feedstock using a hydroprocessing catalyst will tend to cause itscatalytic activity to decline at a rapid rate. This rate of decline incatalytic activity can be an indicator of catalyst stability. A catalystexhibiting a low rate of decline in catalytic activity is thought of ashaving a high stability, and a catalyst exhibiting a high rate ofdecline in catalytic activity is thought of as having a low stability.It is desirable for a catalyst to be highly stable.

The use of ebullating bed reactor systems in the hydrotreatment of aheavy hydrocarbon feedstock has been proposed. In these systems, theheavy hydrocarbon feed is introduced in an upflow direction at thebottom of a catalyst bed contained within a reaction zone in a manner soas to lift or expand the catalyst bed to thereby form a fluidized bed ofthe catalyst. The heavy hydrocarbon passes through the expanded bed ofcatalyst into a separation zone wherein the product is separated fromthe catalyst and liquid hydrocarbon. The liquid hydrocarbon passesthrough a downcomer to a recycle ebullation pump and is recycled andreused in the expansion of the catalyst bed. It is important in theproper operation of the ebullating bed reactor system for the catalystparticles to have a bulk density within a certain range. The bulkdensity must be high enough to avoid substantial carryover of catalystparticles with the separated product but not so high as to requireunreasonably high feed space velocities to provide for bed expansion.

It is also desirable for the hydrotreatment process to provide for theconversion of at least a portion of the heavy hydrocarbon compounds of aheavy hydrocarbon feed to lighter hydrocarbon compounds. There are thosewho have presented various hydrotreatment and hydroconversion catalystcompositions for use in the hydroprocessing of heavy hydrocarbon oils.For instance, WO 00/44856 (Nippon Ketjen and Akzo Nobel) discloses ahydroprocessing catalyst that comprises 7 to 20% of a Group VIB metalcomponent (Mo, W, Cr), 0.5 to 6% Group VIII metal component (Ni, Co,Fe), and 0.1 to 2% alkali metal component supported on a carrier of atleast 3.5% silica and which has a surface area of at least 150 m²/g, atotal pore volume of at least 0.55 ml/g, and a pore size distributionsuch that 30-80% of the pore volume is present in the pores having adiameter of 100-200 Angstroms and at least 5% of the pore volume ispresent in the pores having a diameter of above 1000 Angstroms. Animportant feature of this hydroprocessing catalyst is its silica andsodium content.

U.S. Pat. No. 4,549,957 (Amoco Corporation) discloses a process andcatalyst for the hydrotreating of feeds containing high concentrationsof metals and sulfur. The hydrotreating catalyst comprises ahydrogenation component on a support having specific required physicalproperties including a BET surface area of 150 to 190 m²/g, a porevolume of 0.9 to 1.3 cc/g in the micropores having radii up to 600Angstroms, with at least 0.7 cc/g of such micropore volume in microporeswith radii ranging from 50 to 600 Angstroms, a macropore volume of 0.15to 0.5 cc/g in macropores having radii of 600 to 25,000 Angstroms, and atotal pore volume of 1.05 to 1.8 cc/g. The micropore distribution ofthis catalyst is indicated to be important to its demetalizationactivity, but the precise composition of the support is indicated asbeing relatively unimportant.

U.S. Pat. No. 4,066,574 (Chevron Research Company) discloses ahydrodesulfurization process that uses a catalyst containing a Group VIBmetal and a Group VIII metal on a support material that has at least 70vol. % of its pore volume in pores having a diameter between 80 and 150Angstroms and less than 3 vol % of its pore volume in pores having adiameter above 1000 Angstroms. There is no mention of the surface areaof the catalyst, and the patent states that the support material mayinclude silica suggesting that there is no critical concentrationthereof in the support material.

There is a continuing need to develop hydrotreating catalystcompositions that have improved properties over prior art catalysts suchas better catalytic activity and stability. There is also an ongoingneed to develop improved catalyst compositions and processes thatprovide for the hydrotreating and hydroconversion of heavy hydrocarbonfeedstock.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a new alumina-containingsupport material that is useful as a component of a hydrotreating andhydroconversion catalyst for the hydroconversion of a heavy hydrocarbonfeedstock.

It is another object of the invention to provide a hydrotreating andhydroconversion catalyst that is particularly suitable for use in thehydroconversion of a heavy hydrocarbon feedstock.

Yet, another object of the invention is to provide a process for thehydroconversion of a heavy hydrocarbon feedstock.

Still, another object of the invention is to provide a hydrotreating andhydroconversion catalyst that can suitably be used as the catalystcomponent of an ebullating bed reactor system.

Accordingly, a support material is provided that can suitably be used asa component of a catalyst composition for use in the hydroconversion ofa heavy hydrocarbon feedstock. The support material comprises alumina.The support material further comprises pores having a medium porediameter in the range of from about 100 Angstroms to about 140Angstroms, a pore size distribution width of less than about 33Angstroms, a pore volume of at least 0.75 cc/gram, wherein less than 5percent of the pore volume of the support material is present in thepores having a pore diameter of greater than about 210 Angstroms.

In another invention, a catalyst composition is provided that cansuitably be used for the hydroconversion of a heavy hydrocarbonfeedstock. The catalyst composition comprises a Group VIB metalcomponent, a Group VIII metal component, and a support material. Thesupport material comprises alumina and has a medium pore diameter in therange of from about 100 Angstroms to about 140 Angstroms, a pore sizedistribution width of less than about 33 Angstroms and pore volume of atleast about 0.7 cc/gram.

In yet another invention, provided is a process for the hydroconversionof a heavy hydrocarbon feedstock. The process includes contacting theheavy hydrocarbon feedstock with a hydrotreating and hydroconversioncatalyst composition under suitable hydroconversion process conditions.The hydrotreating and hydroconversion catalyst composition comprises aGroup VIB metal component, a Group VIII metal component, and a supportmaterial. The support material comprises alumina and has a medium porediameter in the range of from about 100 Angstroms to about 140Angstroms, a pore size distribution width of less than about 33Angstroms and pore volume of at least about 0.7 cc/gram.

In still another invention, provided is a method of making an aluminasuitable for an alumina support material. The method comprises the stepsof forming a first aqueous slurry of alumina by mixing, in a controlledfashion, a first aqueous alkaline solution and a first aqueous solutionof a first aluminum compound so as to thereby provide the first aqueousslurry having a first pH in the range of from about 9 to about 10 whilemaintaining a first aqueous slurry temperature in the range of fromabout 25 to 30° C.; thereafter, increasing the first aqueous slurrytemperature to the range of from about 50° C. to 90° C. to provide atemperature adjusted first aqueous slurry; forming a second aqueousslurry, comprising alumina, by adding in a controlled fashion to thetemperature adjusted first aqueous slurry a second aqueous solution of asecond aluminum compound and a second aqueous alkaline solution so as tothereby provide the second aqueous slurry having a second pH in therange of from about 8.5 to 9 while maintaining a second aqueous slurrytemperature in the range of from about 50° C. to 90° C.; and recoveringat least a portion of the alumina of the second aqueous slurry tothereby provide the alumina.

Other objects and advantages of the invention will become apparent fromthe following detailed description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 presents plots of the percent pitch conversion as a function ofcatalyst age for the hydrotreating and hydroconversion catalystcomposition of the invention and a comparative catalyst when used in thehydroconversion of a heavy hydrocarbon feedstock. The plot shows thatthe hydroconversion catalyst composition provides for a significantimprovement in pitch conversion and catalyst stability relative to thecomparative catalyst.

FIG. 2 is a simplified schematic representation of certain aspects ofone embodiment of the inventive process for the hydroconversion of aheavy hydrocarbon feedstock that uses the inventive catalyst in anebullated bed reactor system.

FIG. 3 presents a contour plot for a three-dimensional prediction modelfor predicting the percent pitch conversion advantage for thehydroconversion catalyst composition of the invention when it is used inthe inventive process for the hydroconversion of a heavy hydrocarbonfeedstock. The prediction model is based on the two physical propertyparameters of the hydroconversion catalyst support composition of poresize distribution width (Angstroms) and median pore diameter (Angstroms)that are used to predict the percentage of pitch of a heavy hydrocarbonfeedstock that is converted relative to a comparative catalyst.

DETAILED DESCRIPTION OF THE INVENTION

The inventive hydroconversion catalyst includes a novel alumina supportmaterial that has specifically defined physical properties. It has beenfound that this novel alumina support material provides, when used incombination with a hydrotreating component, for certain unexpectedcatalytic hydroconversion performance properties of the hydroconversioncatalyst when it is used in the hydroconversion of a heavy hydrocarbonfeedstock.

The alumina support material of the hydroconversion catalyst ischaracterized as having a large proportion of its pore volume beingpresent in its pores within a narrow range of pore diameters distributedabout a narrowly defined range of median pore diameters. The aluminasupport material further has a high pore volume and a high surface area.It also can be a desirable feature of the alumina support material tonot contain more than a small concentration of silica such as to affectthe catalytic performance of the hydroconversion catalyst of which thealumina support material is a component.

The references herein to the surface area of the alumina supportmaterial are surface areas as measured by nitrogen adsorption, using thewell-known B.E.T. method. The B.E.T. method of measuring surface areahas been described in detail by Brunauer, Emmet and Teller in J. Am.Chem. Soc. 60 (1938) 309-316, which is incorporated herein by reference.

The references herein to the pore size distribution and pore volume ofthe alumina support material are to those properties as determined bymercury penetration porosimetry. The measurement of the pore sizedistribution of the alumina support material is by any suitable mercuryporosimeter capable of working in the pressure range between atmosphericpressure and about 60,000 PSI, using a contact angle of 140° with amercury surface tension of 474 dyne/cm at 25° C. Pore volume is definedas the total volume using the mercury intrusion method as measuredbetween atmospheric pressure and a pressure of about 60,000 psia. Thereferences herein to median pore diameter (MPD) correspond to the medianpore diameter by volume.

The pore structure of the alumina support material is such that the poresize distribution width is less than about 33 Angstroms. As the term isused herein “pore size distribution width” means the smallest range ofpore diameters of the pores of the alumina support material in which ispresent two-thirds of the total pore volume of the alumina supportmaterial. In order to provide for the best catalyst performance,however, it is better for the pore size distribution width to be withinan even more narrow range of less than 25 Angstroms, and, preferably,less than 22 Angstroms. It is most preferred for the pore sizedistribution width of the alumina support material to be less than 20 Å.

It is also recognized that, in order to provide for the catalyticperformance properties as noted herein, it is important for the medianpore diameter of the pores of the alumina support material to be withinthe narrow range of suitable pore diameters of from about 100 Å to about140 Å. This specific median pore diameter is a particularly importantattribute of the alumina support material component of thehydroconversion catalyst when the hydroconversion catalyst is used inthe hydroconversion of a heavy hydrocarbon feedstock, and, in such aninstance, the median pore diameter of the pores of the alumina supportmaterial can be within the range of pore diameters of from 110 Å to 126Å. Preferably, the median pore diameter of the pores of the aluminasupport material is within the range of pore diameters of from 112 Å to122 Å, and, most preferably, from 114 Å to 120 Å.

The narrow pore distribution of the alumina support material is furtherreflected by the absence of pore volume being present in the largerpores so that less than about 5 percent of the total pore volume of thealumina support material is present in the pores having pore diametersgreater than 210 Å. But, a more important aspect is that it is notdesirable for the alumina support material to include macropores havingpore diameters exceeding 210 Å; since, such pores do not provide for thedesired catalytic benefits required for the hydroconversion of a heavyhydrocarbon feedstock. Thus, in order to maximize the proportion of thealumina support material that provides the desired catalytic benefits,it is best to minimize the amount of pore volume contained in the poreshaving pore diameters exceeding 210 Å. It is, therefore, desirable thatless than 3 percent of the total pore volume of the alumina supportmaterial to be present in the pores having pore diameters greater than210 Å. It is preferred for less than 1.5 percent of the total porevolume of the alumina support material to be in pores of pore diametergreater than 210 Å, and, most preferred, less than 1 percent.

Other physical attributes of the inventive alumina support material arethat it has both a high surface area and a high pore volume. Theseattributes, in combination with the narrow pore size distribution andnarrowly defined median pore diameter, uniquely provide for theinventive hydroconversion catalyst having better catalytic propertiesfor the hydroconversion of a heavy hydrocarbon feedstock thanalternative catalysts. The surface area of the alumina support material,thus, exceeds about 200 m²/g, but, preferably, it exceeds 210 m²/g, and,most preferably, the surface area exceeds 225 m²/g.

The total pore volume of the alumina support material is also relativelyhigh and can be related to the pore size distribution width by thefollowing equation:PV≧0.7+0.004×(w)

wherein PV is the total pore volume of the alumina support material incc/gram; w is the pore size distribution width in Angstroms; and thesymbol ≧ means greater than or equal to. The preferred relationshipbetween the total pore volume (PV) of the alumina support material andthe pore size distribution width (w) is as follows: PV≧0.73+0.004×(w).Thus, in an example of the application of the above equation, if thepore size distribution width of the alumina support material is lessthan 33 Angstroms, the total pore volume of the alumina support materialcan be at least 0.832 cc/gram and, preferably, at least 0.862 cc/gram,or if the pore size distribution width is less than 25 Angstroms, thetotal pore volume can be at least 0.8 cc/gram, and preferably at least0.83 cc/gram, or if the pore size distribution width is less than 22Angstroms, the total pore volume can be at least 0.788 cc/gram and,preferably, at least 0.818 cc/gram, or if the pore size distributionwidth is less than 20 Angstroms, the total pore volume can be at least0.78 cc/gram and preferably at least 0.81 cc/gram. Therefore, the totalpore volume of the novel alumina support material will generally be atleast 0.78 cc/gram or at least 0.79 cc/gram, and, preferably, at least0.81 cc/gram. Most preferably, the total pore volume exceeds 0.83cc/gram.

The hydroconversion catalyst of the invention comprises, consistsessentially of, or consists of a metal component and the alumina supportmaterial. The metal component can include at least one component from aGroup VIB metal component or at least one component from a Group VIIImetal component, or both metal components. It is preferred for thehydroconversion catalyst to comprise both a Group VIB metal componentand a Group VIII metal component. In a further preferred embodiment, thehydroconversion catalyst can further comprise a phosphorous component.

The Group VIII metal component of the hydroconversion catalystcomposition are those Group VIII metal or metal compounds that, incombination with the other components of the catalyst composition,suitably provide a hydroconversion catalyst having the desiredproperties as described herein. The Group VIII metal can be selectedfrom the group consisting of iron, nickel, cobalt, palladium andplatinum. Preferably, the Group VIII metal is either nickel or cobaltand, most preferably, the Group VIII metal is nickel. The Group VIIImetal component contained in the hydroconversion catalyst compositioncan be in the elemental form or in the form of a metal compound, suchas, for example, oxides, sulfides and the like, or mixtures thereof. Theamount of Group VIII metal in the hydroconversion catalyst compositioncan be in the range of from or about 0.5 to or about 6 weight percent,or about 0.5 to about 5 weight percent, elemental metal based on thetotal weight of the hydroconversion catalyst composition. Preferably,for pitch conversion, the concentration of Group VIII metal in thehydroconversion catalyst composition is in the range of from 1.5 weight% to 3 weight %, and, most preferably, the concentration is in the rangeof from 2 weight % to 2.5 weight %.

The Group VIB metal component of the hydroconversion catalystcomposition are those Group VIB metal or metal compounds that, incombination with the other elements of the hydroconversion catalystcomposition, provide a hydroconversion catalyst having the desiredproperties as described herein. The Group VIB metal can be selected fromthe group consisting of chromium, molybdenum and tungsten. The preferredGroup VIB metal is either molybdenum or chromium and, most preferred, itis molybdenum. The Group VIB metal component contained in thehydroconversion catalyst composition can be in the elemental form or inthe form of a metal compound, such as, for example, oxides, sulfides andthe like. The amount of Group VIB metal in the hydroconversion catalystcomposition can be in the range of from or about 4 to or about 22 weightpercent, or about 4 to about 20 weight percent, elemental metal based onthe total weight of the hydroconversion catalyst composition.Preferably, for pitch conversion, the concentration of Group VIII metalin the hydroconversion catalyst composition is in the range of from 6weight % to 12 weight %, and, most preferably, the concentration is inthe range of from 8 weight % to 10 weight %.

In a preferred embodiment, the hydroconversion catalyst compositionfurther includes a phosphorous compound. The concentration ofphosphorous in the hydroconversion catalyst composition can be in therange of from or about 0.05 to or about 6 weight percent, or about 0.05weight percent to about 5 weight percent, elemental phosphorus based onthe total weight of the hydroconversion catalyst composition. But,preferably, the concentration of phosphorous is in the range of from 0.1weight % to about 2 weight %, and, most preferably, from 0.2 to 1.5weight %.

In order to provide a hydroconversion catalyst composition having thedesired improved catalytic properties, it is important for the aluminasupport material to substantially comprise alumina preferably made bythe methods as described herein. It is recognized that the aluminasupport material should also contain no more than a small amount ofsilica due to the negative impact it can have on the catalyticproperties of the final hydroconversion catalyst composition, and, thus,the alumina support material generally should include less than 3 weightpercent silica, preferably, less than 2 weight percent silica, and, mostpreferably, less than 1 weight percent silica.

While the alumina support material can contain small amounts of othercomponents that do not materially affect the properties of thehydroconversion catalyst, the alumina support material should generallycomprise at least 90 weight percent of the alumina as herein described,and, preferably, at least 95 weight percent, and, most preferably,greater than 99 weight percent alumina. The alumina support material,thus, can consist essentially of alumina. The phrase “consistessentially of” as used herein and in the claims with regard to thecomposition of the alumina support material means that the aluminasupport material must contain the alumina and it may contain othercomponents; provided, such other components do not materially influencethe catalytic properties of the final hydroconversion catalystcomposition.

The alumina precursor used in forming the alumina support material ofthe hydroconversion catalyst composition can be from any source or madeby any means or method; provided, however, that the alumina provides forthe specific physical properties and pore structure of the aluminasupport material as fully described herein. One possible method formaking an alumina for use in the alumina support material is describedin U.S. Pat. No. 4,248,852, which is incorporated herein by reference.This method, however, has certain drawbacks in that the requiredsequential and alternate addition of an aluminum compound followed bythe addition of a neutralizing agent to a hydrogel of seed aluminumhydroxide may not necessarily provide for an alumina precursor that hasor can be converted to have the novel physical properties as describedherein for the inventive alumina support material. It is, thus,preferred for the alumina precursor to be made by a two-stepprecipitation process for making an alumina precursor as broadlydescribed in U.S. Pat. No. 6,589,908, which is incorporated herein byreference.

An even more preferred method for preparing the alumina precursor of theinventive alumina support material is a two-step precipitation processused to form an alumina precursor that has or can be converted to havethe novel physical properties necessary for the inventive aluminasupport material.

The first step of the two-step precipitation process includes forming afirst aqueous slurry of alumina by admixing, in a controlled fashionwithin a first precipitation zone, a first aqueous alkaline solution ofat least one alkaline compound selected from the group consisting ofsodium aluminate, potassium aluminate, ammonia, sodium hydroxide, andpotassium hydroxide with a first aqueous acidic solution of at least oneacidic compound selected from the group consisting of aluminum sulfate,aluminum chloride, aluminum nitrate, sulfuric acid, hydrochloric acid,and nitric acid. The mixing of the first aqueous alkaline solution andthe first aqueous acidic solution requires that either the alkalinecompound of the first aqueous alkaline solution or the acidic compoundof the first aqueous acidic solution, or both the alkaline compound andthe acidic compound of such solutions, be a compound containingaluminum. For example, the alkaline compound of the first aqueousalkaline solution that is an aluminum containing compound is eithersodium aluminate or potassium aluminate, and the acidic compound of thefirst aqueous acidic solution that is an aluminum containing compound iseither aluminum sulfate or aluminum chloride or aluminum nitrate.

The first aqueous alkaline solution and the first aqueous acidicsolution are mixed together, in a well mixed tank and in a controlledmanner, in such proportions as to thereby maintain a first pH of theresulting first aqueous slurry in the range of from about 8 to about 11.The first aqueous alkaline solution and the first aqueous acidicsolution are also admixed together in such quantities as to therebyprovide the first aqueous slurry that contains a first desired amount ofalumina that is in the range of from about 25 weight % to about 35weight % of the total alumina made by the two-step precipitationprocess. The temperature within the first precipitation zone and atwhich the mixing step is conducted is maintained or controlled at afirst aqueous slurry temperature in the range of from about 20° C. toabout 40° C., preferably, from 25 to 30° C.

When the first desired amount of alumina has been formed in the firststep, the temperature of the resulting first aqueous slurry isthereafter increased from the first aqueous slurry temperature to atemperature adjusted first aqueous slurry temperature that is in therange of from about 45° C. to about 70° C., preferably, from 50 to 65°C. This raising of the temperature of the first aqueous slurry can bedone by heating the first aqueous slurry either while it is containedwithin the first precipitation zone or as it is transferred into asecond precipitation zone or after it has been transferred into andwhile it is contained within the second precipitation zone.

The second step of the two-step precipitation process can be conductedeither in the first precipitation zone or in a second precipitationzone. It is preferred to transfer the first aqueous slurry, which hasbeen heated to the temperature adjusted first aqueous slurrytemperature, to the second precipitation zone wherein the second step ofthe two-step precipitation process is conducted.

A second aqueous slurry is thus formed by admixing in a controlledfashion, and, preferably, within a second precipitation zone with thetemperature adjusted first aqueous slurry, a second aqueous alkalinesolution of at least one alkaline compound selected from the groupconsisting of sodium aluminate, potassium aluminate, ammonia, sodiumhydroxide, and potassium hydroxide and a second aqueous acidic solutionof at least one compound selected from the group consisting of aluminumsulfate, aluminum chloride, aluminum nitrate, sulfuric acid,hydrochloric acid, and nitric acid. The mixing of the second aqueousalkaline solution and the second aqueous acidic solution requires thateither the alkaline compound of the second aqueous alkaline solution orthe acidic compound of the second aqueous acidic solution, or both thealkaline compound and the acidic compound of such solutions, be acompound containing aluminum. For example, the alkaline compound of thesecond aqueous alkaline solution that is an aluminum containing compoundis either sodium aluminate or potassium aluminate, and the acidiccompound of the second aqueous acidic solution that is an aluminumcontaining compound is either aluminum sulfate or aluminum chloride oraluminum nitrate.

The second aqueous alkaline solution and the second aqueous acidicsolution are admixed with the first aqueous slurry in the second step ofthe two-step precipitation process in such amounts and proportions as tothereby provide the second aqueous slurry having a second pH in therange of from about 8 to 10.5. Also, the second aqueous alkalinesolution and the second aqueous acidic solution are admixed with thefirst aqueous slurry in such quantities as to form the remaining amountof alumina made by the two-step precipitation process. The temperatureat which the adding step is conducted is maintained or controlled sothat a second aqueous slurry temperature is in the range of from about45° C. to about 70° C., preferably, from 50 to 65° C. The aluminaconcentration in the final second aqueous slurry should be such thatfrom about 4 weight percent to about 8 weight percent of the totalweight thereof is alumina (on an Al₂O₃ basis), based on the aluminaprecipitate being calcined. Preferably, the final second aqueous slurrycontains from 6 weight percent to 6.5 weight percent alumina (oncalcined basis).

The prepared alumina precursor formed in the two-step precipitationprocess has special physical properties which permit its use as acomponent of the alumina support material, as described herein, and theprepared alumina precursor comprises alumina in the form ofpseudo-boehmite. More particularly, the prepared alumina precursor madeby the two-step precipitation process comprises substantially entirelypseudo-boehmite wherein the alumina comprises at least 90 weight percentthereof pseudo-boehmite, but, preferably, the form of the alumina of theprepared alumina precursor comprises at least 95 weight percentpseudo-boehmite and, more preferably, at least 98 weight percentpseudo-boehmite. Furthermore, the prepared alumina can comprise lessthan 3 weight percent silica, preferably, less than 2 weight percentsilica, and most preferably, less than 1 weight percent silica.

The prepared alumina precursor that is particularly suitable for use asa component in the manufacture of the alumina support material has ahigh meso pore volume. The mesopore volume of the prepared aluminaprecursor powder when it is dried and calcined at 1100 F for an hour isgreater than 0.89 cc/g, preferably greater than 0.90 cc/g, mostpreferably greater than 0.92 cc/g. The mesopore volume is the porevolume in the pores having diameters less than 210 Å as measured bymercury porosimetry. The prepared alumina precursor can yield an aluminasupport material which exhibits a single-modal pore volume distributioncharacteristic in that no more than one maximum can be observed when theincremental pore volume of the prepared alumina is plotted as a functionof pore diameter of the prepared alumina. The surface area of theprepared alumina precursor can exceed 200 m²/g.

The preferred alkaline compound for use in forming both the firstaqueous alkaline solution and the second aqueous alkaline solution issodium aluminate. Generally, the concentration of the sodium aluminatesolution is in the range of about 25 to about 45 weight percent sodiumaluminate.

The preferred acidic compound for use in forming both the first aqueousacidic solution and the second aqueous acidic solution is aluminumsulfate. It is preferred for the aluminum sulfate concentration toapproach saturation in the water. The alumina contained in the secondaqueous slurry is recovered therefrom by any suitable method or meansknown to those skilled in the art. Suitably, the final alumina of thesecond aqueous slurry is filtered and washed with any suitable solvent,for example, water, in accordance with methods known to those skilled inthe art in order to remove from the filter cake water solublecontaminants such a sodium, sulfate, chloride, and the like. The washedfilter cake can be used directly in the preparation of the aluminasupport material or it can be dried to produce a powder of alumina thatis used in the preparation of the alumina support material. The filtercake can be dried by any suitable method or means known to those skilledin the art, such as, for example, tray drying, belt drying, flash dryingor spray drying. A preferred method that can be used to provide asuitable alumina for use in forming the alumina support material is tospray dry or flash dry a slurry of the alumina obtained from the secondaqueous slurry, after proper washing.

The manufacturing method and conditions by which the alumina supportmaterial is made are important to providing the alumina support materialhaving the physical properties as described herein and which arenecessary to provide the hydroconversion catalyst that has the improvedcatalytic properties as described herein. One feature of the inventioncan include the combined use of the alumina precursor made by thetwo-step precipitation process along with the method of manufacturingthe alumina support material using the alumina precursor to provide analumina support material having the precise physical properties asdescribed herein which make it especially suitable for use in thehydroconversion catalyst of the invention.

In a preferred method to prepare the alumina support material, theprepared alumina is mixed or mulled, with water and a dilute acid toform a paste that can be formed into agglomerate particles such asextrudates. Any suitable method or means known to those skilled in theart can be used to form the agglomerate particles, but known extrusionmethods are preferred. The extrudate of the alumina support material isformed by extruding the paste through an extrusion die having openingsof desired size and shape. The extrudates can be cylindrical in shapeand have a diameter in the range of from about 0.5 mm to about 3.0 mm.

It can be important in the preparation of the particles of aluminasupport material for the pH of the paste formed by mixing the water,dilute acid, and alumina to be controlled within a certain range. Thisis in order to provide a final alumina support material for use in thehydroconversion catalyst having the novel physical properties asdescribed herein. The pore size distribution of the final aluminasupport material is in part controlled by the pH, with a lower pHproviding for a sharper pore size distribution as required for theinvention. Thus, the pH of the paste of alumina should be in the rangeof from about 5 to about 9, but, preferably, the pH can be in the rangeof from 6 to 8.

The formed particle of alumina support material, after drying by anysuitable means or method known to those skilled in the art, is heattreated, or calcined, to provide the final alumina support material. Thedried, formed particle of alumina support material is preferablycalcined in the presence of oxygen or an oxygen containing inert gas orair. While the proper calcination time and calcination temperature candepend on the particular equipment used in the calcination, theproduction rate of catalyst particles and the desired median pore size,the temperature at which the dried, formed particle of alumina supportmaterial is calcined generally is in the range of from 371° C. (700° F.)to about 760° C. (1400° F.). Preferably, the calcination temperature isin the range of from 482° C. (900° F.) to 732° C. (1350° F.), and, morepreferably, it is from 399° C. (950° F.) to 704° C. (1300° F.). The timerequired for the calcination is generally in the range of from about 0.5hours to about 4 hours.

The calcination provides, among other things, the conversion of thepseudo-bohemite alumina into predominantly gamma alumina. Thus, thealumina of the alumina support material will comprise gamma alumina in apredominant amount wherein the alumina component of the alumina supportmaterial can comprise at least 90 weight percent gamma alumina.Preferably, the alumina comprises at least 95 weight percent gammaalumina and, most preferably, at least 98 weight percent. Any suitableequipment such as a direct fire kiln, an indirect fire rotary calcineror a moving belt calcination system can be used to calcine the dried,formed particle of alumina support material.

The metal components of the hydroconversion catalyst are incorporatedinto the alumina support material by any suitable means or method knownto those skilled in the art. For instance, the metal and phosphorouscomponents can be co-mulled with the alumina of the alumina supportmaterial during the formation of the agglomerate particles of thealumina support material, or the metal and phosphorous components can beincorporated into the alumina support material by impregnation, or themetal and phosphorous can be incorporated into the alumina supportmaterial by a combination of methods. It is preferred, however, to usean impregnation procedure to impregnate the alumina support materialwith one or more of the catalytic components as described herein.

Suitable impregnation procedures include, for example, sprayimpregnation, soaking, multi-dip procedures, and incipient wetnessimpregnation methods. An impregnation solution comprising either a GroupVIII metal compound, or a Group VIB metal compound, or a phosphorouscompound, or any combination of such compounds, dissolved in a suitableliquid solvent, such as water, alcohol, or liquid hydrocarbon is used toimpregnate the alumina support material with the catalytic components.The catalytic components are incorporated into the alumina supportmaterial in such amounts as to provide the concentration of metalcomponents as described above. The alumina support material with theincorporated hydrogenation components can be dried, or calcined, orboth, in accordance with known methods to provide the hydroconversioncatalyst.

The novel hydroconversion catalysts described herein can be usedadvantageously for the hydrotreating and hydroconversion of a heavyhydrocarbon feedstock; and, in fact, the hydroconversion catalystsprovide for superior results in the hydroconversion of the pitchfraction of a heavy hydrocarbon feedstock.

The hydroconversion catalyst, when in the form of a shaped particle suchas a sphere or a pill or an extrudate, but, preferably, an extrudate,can be a particularly superior and beneficial catalyst when used in anebullated bed reactor system for the hydroprocessing a heavy hydrocarbonfeedstock. The shaped or formed particle of the hydroconversion catalystcomposition can, thus, have density properties such that they provide abulk density that makes the shaped or formed particle of thehydroconversion catalyst composition effective for the use in anebullated reactor bed for the hydroconversion of a heavy hydrocarbonfeedstock.

The bulk density of the shaped or formed particle of the hydroconversioncatalyst can be within a broad range that permits its use in a widearray of catalytic processes such as fixed bed, fluidized bed andebullated bed processes. The bulk density of the shaped or formedparticles of the hydroconversion catalyst makes them particularlysuitable for use in an ebullated reactor bed system.

The heavy hydrocarbon feedstock of the inventive process can be obtainedfrom any suitable source of hydrocarbons, including, for example,petroleum crude oils and tar sand hydrocarbons, such as, the heavy oilsextracted from tar sand. The heavy hydrocarbon feedstock can be a vacuumresid or atmospheric resid component of a petroleum crude oil or a tarsand hydrocarbon.

The heavy hydrocarbon feedstock can further include high concentrationsof sulfur and nitrogen compounds and metals, such as, nickel andvanadium. Indeed, it is the high concentrations of metal, sulfur andnitrogen compounds in addition to the high molecular weight of the heavyhydrocarbon feedstock that make its hydrotreatment so challenging.

The heavy hydrocarbon feedstock, thus, includes a mixture ofhydrocarbons derived from a crude oil or tar sand hydrocarbon materialor other source of heavy hydrocarbons. A portion, preferably a majorportion, of the heavy hydrocarbons of the mixture has a boilingtemperature exceeding about 343° C. (650° F.). The heavy hydrocarbonfeedstock is thus defined as having a boiling range, as determined byASTM test procedure D-1160, such that at least about 30 weight percentof the heavy hydrocarbon feedstock boils at a temperature exceeding 524°C. (975° F.). The preferred heavy hydrocarbon feedstock has a boilingrange such that at least 40 weight percent boils at a temperatureexceeding 524° C. (975° F.), and, most preferably, at least 50 weightpercent of the heavy hydrocarbon feedstock boils at a temperatureexceeding 524° C. (975° F.).

The API gravity of the heavy hydrocarbon feedstock can range from about3 to about 20, but, more specifically, the API gravity is in the rangeof from 4 to 15, and, more specifically, from 4 to 11.

The heavy hydrocarbon feedstock can have a Conradson carbon content, asdetermined by ASTM testing method D-189, exceeding 5 weight percent,and, more specifically, the Conradson carbon content is in the range offrom 8 weight percent to 30 weight percent.

The heavy hydrocarbon feedstock can also comprise sulfur compounds inamounts such that the concentration of sulfur in the heavy hydrocarbonfeedstock exceeds about 2 weight percent and even exceeds 3 weightpercent. More specifically, the sulfur concentration in the heavyhydrocarbon feedstock can be in the range of from 4 to 10 weightpercent. The heavy hydrocarbon feedstock can further comprise nitrogencompounds in amounts such that the concentration of nitrogen in theheavy hydrocarbon feedstock exceeds 0.1 weight percent and even exceeds0.2 weight percent. More specifically, the nitrogen concentration in theheavy hydrocarbon feedstock can be in the range of from 0.3 to 3 weightpercent.

As earlier noted, the metals contained in the heavy hydrocarbonfeedstock can include nickel or vanadium, or both. The nickelconcentration in the heavy hydrocarbon feedstock can exceed 10 parts permillion by weight (ppmw) or it can exceed 30 ppmw. More specifically,the nickel concentration in the heavy hydrocarbon feedstock can be inthe range of from 40 ppmw to 500 ppmw. The vanadium concentration in theheavy hydrocarbon feedstock can exceed 50 ppmw or it can exceed 100ppmw. More specifically, the vanadium concentration in the heavyhydrocarbon feedstock can be in the range of from 150 ppmw to 1500 ppmw.

The process of the invention includes contacting the heavy hydrocarbonfeedstock, preferably in the presence of hydrogen, with thehydroconversion catalyst under suitable hydroprocessing conditions. Oneimportant aspect of the inventive process is that it provides for anexceptionally high percentage conversion of the pitch component of theheavy hydrocarbon feedstock, especially when compared to the conversionsprovided by certain other catalysts and processes.

As used herein, the term “pitch” refers to the hydrocarbon moleculescontained in the fraction of the heavy hydrocarbon feedstock that boilat temperatures above 524° C. (975° F.). The references herein to “pitchconversion” or similar references to the conversion of pitch, arespeaking of the cracking of the heavy hydrocarbon molecules that make upthe pitch component of the heavy hydrocarbon feedstock to smallerhydrocarbon molecules that boil at temperatures below 524° C. (975° F.).

The percent conversion of pitch is then defined as being the weightpercent of the pitch contained in the heavy hydrocarbon feedstock thatis converted by the hydroconversion process, and it can be representedby the ratio of the difference between the weight of pitch in a feed andthe weight of pitch in the product with the difference divided by theweight of pitch in the feed with the resulting ratio being multiplied by100 to provide the percentage pitch conversion.

The hydroconversion process can be carried out by the use of anysuitable reaction means or system including fixed bed, moving bed,fluidized bed and ebullated bed reactor systems. While thehydroconversion catalyst can be used as a part of any suitable reactorsystem, its properties make it particularly suitable for use inebullated bed systems. For instance, the hydroconversion catalyst can beformed into particles that provide for a bulk density which make thehydroconversion catalyst especially effective for use as the catalystcomponent of an ebullated bed system.

The hydroprocessing conditions under which the heavy hydrocarbonfeedstock is contacted with the hydroconversion catalyst include thoseprocess conditions that are effective in providing for a hydrotreatedproduct and, preferably, that are effective in the conversion of atleast a portion of the pitch component of the heavy hydrocarbonfeedstock. The conversion of the pitch component can exceed about 50weight percent of the pitch. Higher pitch conversion is desirable and,thus, preferably, pitch conversion exceeds 55 weight percent, and, mostpreferably, pitch conversion exceeds 60 weight percent.

The inventive hydroconversion catalyst can suitably provide a high pitchconversion, since the activity of the fresh hydroconversion catalyst forthe conversion of pitch of a heavy hydrocarbon feedstock can exceedabout 58 weight percent and even exceed about 60 weight percent. Thepreferred hydroconversion catalyst can even have a pitch conversionactivity in its fresh state exceeding 62 weight percent, and, mostpreferred, exceeding 64 weight percent. The weight percent conversion ofpitch is defined as the conversion as measured using the testingprocedure as described in Example 5 herein.

Suitable hydroprocessing conditions under which the heavy hydrocarbonfeedstock is contacted with the hydroconversion catalyst can include ahydroconversion contacting temperature in the range of from about 316°C. (6000° F.) to about 538° C. (1000° F.), a hydroconversion totalcontacting pressure in the range of from about 500 psia to about 6,000psia, which includes a hydrogen partial pressure in the range of fromabout 500 psia to about 3,000 psia, a hydrogen addition rate per volumeof heavy hydrocarbon feedstock in the range of from about 500 SCFB toabout 10,000 SCFB, and a hydroconversion liquid hourly space velocity(LHSV) in the range of from about 0.2 hr⁻¹ to 5 hr⁻¹.

The preferred hydroconversion contacting temperature is in the range offrom 316° C. (600° F.) to 510° C. (950° F.), and, most preferred, from371° C. (700° F.) to 455° C. (850° F.). The preferred hydroconversiontotal contacting pressure is in the range of from 500 psia to 2,500psia, most preferably, from 500 psia to 2,000 psia, with a preferredhydrogen partial pressure of from 800 psia to 2,000 psia, and mostpreferred, from 1,000 psia to 1,800 psia. The LHSV is preferably in therange of from 0.2 hr-1 to 4 hr-1, and, most preferably, from 0.2 to 3hr-1. The hydrogen addition rate is preferably in the range of from 600SCFB to 8,000 SCFB, and, more preferably, from 700 SCFB to 6,000 SCFB.

Presented in FIG. 6 is a simplified schematic representation of anebullated bed reactor system 10. The ebullated bed reactor systemincludes elongated vessel 12 that defines several zones such as acontacting zone for contacting a heavy hydrocarbon feedstock undersuitable hydroconversion reaction conditions with a hydroconversioncatalyst and a separation zone for the separation of a hydrotreatedheavy hydrocarbon product from the hydroconversion catalyst.

Within elongated vessel 12 is a settled hydroconversion catalyst bed 14having a settled hydroconversion catalyst bed level 16. A reactor feedcomprising heavy hydrocarbon feedstock and hydrogen is introduced intoelongated vessel 12 by way of conduit 18. The reactor feed passesthrough horizontal distributor plate 20 that provides means fordirecting the reactor feed upwardly and through settled hydroconversioncatalyst bed 14. The passing of the reactor feed through settledhydroconversion catalyst bed 14 serves to lift and to expand thehydroconversion catalyst to thereby provide an expanded hydroconversioncatalyst bed 22 (ebullated catalyst bed) having an expandedhydroconversion catalyst bed level 24.

In separation zone 26 of elongated vessel 12, hydroconversion catalystis separated from liquid hydrocarbon 28, having a liquid level 30, andthe product from the hydrotreatment of the heavy hydrocarbon feedstock,which passes from elongated vessel 12 by way of conduit 32.

Downcomer 34 within elongated vessel 12 provides conduit means forrecycling the liquid hydrocarbon 28 to the bottom of expandedhydroconversion catalyst bed 22. Conduit 36 is operatively connected influid flow communication between downcomer 34 and ebullating pump 38.Ebullating pump 38 provides means for recycling and circulating theliquid hydrocarbon 28 through expanded hydroconversion catalyst bed 22.

The upper end of elongated vessel 12 includes catalyst inlet conduitmeans 40, which provides for the introduction of fresh hydroconversioncatalyst while ebullated bed reactor system 10 is in operation. Freshhydroconversion catalyst can be introduced into elongated vessel 12through conduit means 40 by way of conduit 42. The lower end ofelongated vessel 12 includes catalyst outlet conduit means 44, whichprovides for the removal of spent hydroconversion catalyst whileebullated bed reactor system 10 is in operation.

The hydroconversion catalyst of the invention is particularly suitablefor use in an ebullated bed reactor system which in certain instancescan provide advantages over other types of reactor systems, for example,fixed bed reactor systems. Ebullated bed reactor systems are especiallysuitable for the hydroconversion of heavy hydrocarbon feedstocks;because, they enable an operation at the higher process temperatures andpressures generally required for the hydroprocessing of heavyfeedstocks, and they permit the addition and withdrawal of thehydroconversion catalyst without requiring reactor shutdown.

The following Examples are presented to illustrate the invention, butthey should not be construed as limiting the scope of the invention.

EXAMPLE 1

This Example 1 describes, generally, the laboratory preparation of thealuminum powder used to make the catalyst substrates that were used asthe alumina support material in the preparation of the hydroconversioncatalyst of the invention. This Example also presents the specificpreparation conditions under which the alumina powders A, B, C, D and Ewere prepared using the generally described preparation procedure.

The alumina used for the catalyst substrate was made by a two-stepprecipitation process. The first step includes forming a first aqueousslurry of alumina by mixing a first aqueous alkaline solution of sodiumaluminate with a first aqueous acidic solution of aluminum sulfate. Thefirst aqueous alkaline solution and the first aqueous acidic solutionwere mixed in such amounts as to provide the first aqueous slurry thathas a first pH and which contained a first amount of alumina(precipitate) as a percent of the total alumina made by the two-stepprecipitation process. The first step was conducted at a firstprecipitation temperature.

When the desired first amount of alumina was formed in the first step,the temperature of the resulting first aqueous slurry was thereafterincreased to a second precipitation temperature. A second aqueous slurrywas thereafter formed by adding, in a controlled fashion, to the firstaqueous slurry both a second aqueous acidic solution aluminum sulfateand a second aqueous alkaline solution of sodium aluminate so as tothereby provide the second aqueous slurry having a second pH and to formthe remaining amount of alumina made by the two-step precipitationprocess. The second step was conducted at the second precipitationtemperature. The alumina contained in the second aqueous slurry wasrecovered, washed, dried and used in the preparation of the extrudatesof Example 2.

Table 1 presents the preparation conditions under which each of thealumina powders A through E were made.

TABLE 1 Conditions Used in the Two-Step Preparation of Alumina PowdersA, B, C, D and E Alumina Powder Preparation 1st Step Conditions Alumina2nd Step Conditions in first Final Alumina First step/total Second Al₂O₃Powder First Temp alumina Second Temp concentration Sample pH (° C.) (%)pH (° C.) (%) A 8.9 30 35 8.7 60 6.0 B 9.1 30 30 8.7 60 6.2 C 9.1 31 318.7 60 6.3 D 8.8 30 30 8.7 60 6.1 E 9.3 27 30 8.7 57 6.1

EXAMPLE 2

This Example 2 describes the general laboratory procedure for thepreparation of the catalyst substrates (i.e., alumina-containingextrudates) that were used in the preparation of the hydroconversioncatalysts of the invention. Also presented are the specific preparationconditions under which the extrudates A, B, C, D and E were preparedusing the generally described procedure.

Each of the alumina powder materials described in Example 1 were mixedwith water and a dilute nitric acid to form a suitable extrudable paste.The extrudable paste was formed into cylindrical extrudates having anominal diameter of 0.8 mm. The extrudates were dried at a dryingtemperature followed by calcination at a calcination temperature. Table2 presents the preparation conditions for each of the extrudates alongwith the % loss on ignition (% LOI) values. The extrudate Samples Athrough E respectively were derived from corresponding alumina powderSamples A through E.

TABLE 2 Conditions Used in the Preparation of Extrudate Samples AThrough E Extrudate Preparation Calcination Extrudate Acid Conc TempSample (wt %) LOI (%) (° C.) A 0.5 63.3 654 B 1.5 63.5 593 C 0.5 63.8649 D 0.5 64.2 760 E 0.5 64.0 565

EXAMPLE 3

This Example 3 presents certain of the important physical properties ofeach of the extrudate samples of Example 2 and of a comparison catalystthat is a commercially available hydroprocessing catalyst.

TABLE 3 Physical Properties of Extrudates A Through E and ComparisonPhysical Properties of Extrudates Mercury Median Pore Surface Pore PoreSize Extrudate Volume Area Diameter Distribution Sample (cc/g) (m²/g)(Å) Width (Å) Comp. 0.84 255 122 36 Catalyst A 0.78 227 119 18 B 0.89251 119 22 C 0.85 224 127 26 D 0.84 221 127 20 E 0.81 235 108 20

EXAMPLE 4

This Example 4 describes the laboratory impregnation procedure used toimpregnate the extrudates of Example 3, with the catalytic components(i.e., Group VIII metal component, Group VIB metal component, andphosphorous component) and the further treatment of the impregnatedcatalyst substrate to provide the final hydroconversion catalyst of theinvention. Each of the metal impregnations of the catalyst substrate wasthe same.

For 200 g of calcined alumina extrudate an impregnation solution wasprepared by adding 31.76 g of molybdenum oxide (assay: 66.26%molybdenum), 12.63 g of nickel carbonate (assay: 40.24% nickel) and 6.3g of phosphoric acid solution (assay: 16.86% phosphorus) to about 200 mlof water, heating the mixture close to its boiling point until all thesolids were dissolved, and then adjusting the solution volume (by eitherboiling off water or adding water) to the exact pore volume of the 200 gof calcined alumina extrudate. This solution was added to the calcinedalumina extrudate, and the thus-impregnated calcined alumina extrudatewas aged for a minimum of 2 hours, and then dried at 100° C. for 4 hoursminimum, followed by calcination in air at 538° C. for 90 minutes. Thefinal metal loadings of the catalysts A, B, C, D and E and the metalloadings of the comparative catalyst include 8.7 wt % molybdenum (asmetal), 2.1 wt % nickel (as metal), and 0.7 wt % phosphorous(elemental).

EXAMPLE 5

This Example 5 describes the experimental testing procedure and testingconditions used to test the hydrotreating and hydroconversionperformance properties of a comparison catalyst of Example 3 and of thehydroconversion catalysts A through E of Example 4.

Each of the catalysts A through E and the commercially availablecomparison catalyst were tested for their catalytic performance in thehydroprocessing and hydroconversion of a heavy hydrocarbon feed havingthe composition and properties presented in Table 4 below. The testspresented in this Example 5 were conducted in a continuous stirred tankreactor (CSTR) using a laboratory autoclave equipped with a standard,commercially available Robinson-Mahoney stationary catalyst basket. Thereactor was filled with 138 cc of the relevant catalyst, and the reactorwas charged with the heavy hydrocarbon feed at a rate of 150 g/hour andwith hydrogen at a rate of 97.1 standard (temperature is 25° C.,pressure is 1 atm.) liters per hour. The reaction conditions weremaintained at 1500 psia and 423° C.

TABLE 4 Heavy Hydrocarbon Feed Properties and Composition Density (g/ml)1.0172 Sulfur (wppm) 48132 Nitrogen (wppm) 4530 Carbon (wt %) 82.98Hydrogen (wt %) 10.36 Toluene Insolubles (wt %) 0.42 MCR (wt %) 14.12 Ni(ppm) 90.1 V (ppm) 237 IBP-524, wt. % 42.45 524+, wt. % 56.37

The product was recovered and the composition thereof was determinedwhich permitted a determination of the percent conversion of the pitchcomponent of the feed. The results of the performance testing ofcatalyst A, as compared to the comparison catalyst are presentedgraphically, in FIG. 1, to illustrate the data generated in this study.Also presented in Table 5 below is the calculated average pitchconversion of each of the catalysts and the improvement in pitchconversion that the inventive catalysts present relative to thecomparison catalyst.

TABLE 5 Pitch Conversion Provided by Catalysts Average Pitch Delta FromCatalyst Conversion (%) Comparison Comparison 59.7 0 Catalyst A 63.2 3.5B 62.7 3.0 C 60.7 1.0 D 62.2 2.4 E 61.8 2.1

The results from these tests show that the inventive catalysts havecomparable stability to that of the comparison catalyst, but theyprovide significantly higher pitch conversion. Further demonstrated isthat certain of the inventive catalysts that have particularly narrowpore size distribution widths and specific mean pore diameters providefor even greater pitch conversion than those having wider pore sizedistribution widths and mean pore diameters outside a specific ranges.

EXAMPLE 6

Certain of the unexpected features of the inventive catalysts aredepicted in FIG. 3 as a prediction model, which provides for theprediction of the percent conversion advantage that the inventivecatalysts provide over the comparative catalyst.

The prediction model is a proprietary model that utilizes an extensivedatabase of information and can be used to predict the pitch conversionadvantage provided by the inventive catalyst based on the two physicalproperty parameters of pore size distribution width and median porediameter when the inventive catalysts are used in the hydroconversion ofa heavy feedstock. The model of FIG. 3 is presented to illustrate thesignificance of the narrow pore size distribution width and median porediameter in providing for high pitch conversion and pitch conversionadvantage. Pitch conversion advantage is defined as the differencebetween the percent conversion of pitch that the relevant catalyst andthe comparison catalyst provide when processing the same feed under thesame reaction testing conditions.

Reasonable variations, modifications and adaptations of the inventioncan be made within the scope of the described disclosure and theappended claims without departing from the scope of the invention.

That which is claimed is:
 1. A support material suitable for use as acomponent of a catalyst composition for use in the hydroconversion of aheavy hydrocarbon feedstock, said support material consists essentiallyof: alumina; wherein said support material has a single-modal porevolume characteristic and comprises pores having a median pore diameterin the range of from 110 Angstroms to 126 Angstroms, a pore sizedistribution width of less than 33 Angstroms, a pore volume that isrelated to said pore size distribution width such that said pore volume(PV) is greater than or equal to a value as determined by 0.7 +0.004 x(w) wherein (w) is said pore size distribution width in Angstroms ofsaid support material, and wherein less than 5 percent of said porevolume is present in said pores having a pore diameter of greater thanabout 210 Angstroms and wherein said support material includes no morethan a small concentration of silica.
 2. A support material as recitedin claim 1, wherein said small concentration of silica is less than 3weight percent of said support material.
 3. A support material asrecited in claim 2, wherein said alumina is made by the methodcomprising the steps of: forming a first aqueous slurry of alumina bymixing, in a controlled fashion, a first aqueous sodium aluminatesolution and a first aqueous solution of aluminum sulfate so as tothereby provide said first aqueous slurry having a first pH in the rangeof from about 9 to about 10 while maintaining a first aqueous slurrytemperature in the range of from about 25 to 30° C.; thereafter,increasing said first aqueous slurry temperature to the range of fromabout 45 ° C. to 70° C. to provide a temperature adjusted first aqueousslurry; forming a second aqueous slurry, comprising alumina, by addingin a controlled fashion to said temperature adjusted first aqueousslurry a second aqueous solution of a second aluminum compound and asecond aqueous alkaline solution so as to thereby provide said secondaqueous slurry having a second pH in the range of from about 8.5 to 9while maintaining a second aqueous slurry temperature in the range offrom about 45° C. to 70° C.; and recovering at least a portion of saidalumina of said second aqueous slurry and utilizing the thus-recoveredalumina as said alumina of said support material.
 4. A support materialas recited in claim 2, wherein the median pore diameter of the pores ofthe alumina support material is in the range of from 112 Angstroms to122 Angstroms.
 5. A support material as recited in claim 4, wherein thepore size distribution is less than 25 Angstroms.
 6. A support materialas recited in claim 2, wherein the median pore diameter of the pores ofthe alumina support material is in the range of from 114 Angstroms to120 Angstroms.
 7. A support material as recited in claim 6, wherein thepore size distribution is less than 20 Angstroms.
 8. A method of makingan alumina suitable for an alumina support material, said methodcomprising a two-step precipitation process which comprises the stepsof: forming a first aqueous slurry of alumina by mixing, in a controlledfashion, a first aqueous sodium aluminate solution and a first aqueoussolution of aluminum sulfate in such proportions so as to therebyprovide said first aqueous slurry that contains a desired amount of from25 weight percent to 35 weight percent of the total amount of the totalalumina made by the two-step precipitation process, and having a firstpH in the range of from about 9 to about 10while maintaining a firstaqueous slurry temperature in the range of from about 25 to 30 ° C.;thereafter, when the first desired amount of alumina has been formed,increasing said first aqueous slurry temperature to the range of fromabout 45° C. to 75° C. to provide a temperature adjusted first aqueousslurry; forming a second aqueous slurry, comprising alumina, by addingin a controlled fashion to said temperature adjusted first aqueousslurry a second aqueous solution of a aluminum sulfate and a secondaqueous sodium aluminate solution so as to thereby provide said secondaqueous slurry that contains an alumina concentration of from 4 weightpercent to 8 weight percent of the total weight of the alumina, based onthe alumina precipitate being calcined, and having a second pH in therange of from about 8.5 to 9 while maintaining a second aqueous slurrytemperature in the range of from about 50° C. to 65° C.; recovering atleast a portion of said alumina of said second aqueous slurry to therebyprovide an alumina precursor, comprising at least 90 weight percentpseudo-boehmite, and having a high mesopore volume and a surface areaexceeding 200 m²/g; and mixing said alumina precursor with water and adilute acid to form a paste having a pH in the range of from about 5 toabout 9 and forming said paste into a particle and calcining saidparticle to thereby provide an alumina support material, which comprisesat least 90 weight percent gamma alumina and less than 3 weight percentsilica, and wherein said alumina support material has a single-modalpore volume distribution characteristic, pores having a median porediameter in the range of from 110 Angstroms to 126 Angstroms, a poresize distribution width of less than 33 Angstroms, a pore volume that isrelated to said pore size distribution width such that said pore volume(PV) is greater than or equal to a value as determined by 0.7 +0.004 x(w) wherein (w) is said pore size distribution width in Angstroms ofsaid alumina support material, wherein less than 5 percent of said porevolume is present in said pores having a pore diameter of greater thanabout 210 Angstroms.
 9. A method as recited in claim 8, furthercomprising: incorporating a hydrogenation component into said heattreated shaped particle to provide a hydroconversion catalyst, whereinsaid hydrogenation component is selected from the group of compoundsconsisting of Group VIII metal components, Group VIB metal components,phosphorous components and any combination thereof.
 10. A method asrecited in claim 8, wherein the pH of the paste is in the range of from6 to
 8. 11. A method of making a composition, said method comprising atwo-step precipitation process which comprises the steps of: forming afirst aqueous slurry of alumina by mixing, in a controlled fashion, afirst aqueous sodium aluminate solution and a first aqueous solution ofaluminum sulfate so as to thereby provide said first aqueous slurry thatcontains a desired amount of from 25 weight percent to 35 weight percentof the total amount of the total alumina made by the two-stepprecipitation process, and having a first pH in the range of from about9 to about 10 while maintaining a first aqueous slurry temperature inthe range of from about 20 to 40 ° C.; thereafter, increasing said firstaqueous slurry temperature to the range of from about 45° C. to 70° C.to provide a temperature adjusted first aqueous slurry; forming a secondaqueous slurry, comprising alumina, by adding in a controlled fashion tosaid temperature adjusted first aqueous slurry a second aqueous solutionof aluminum sulfate and a second aqueous sodium aluminate solution so asto thereby provide said second aqueous slurry that contains an aluminaconcentration of from 4 weight percent to 8 weight percent of the totalweight of the alumina, based on the alumina precipitate being calcined,and having a second pH in the range of from about 8.5 to 9 whilemaintaining a second aqueous slurry temperature in the range of fromabout 45° C. to 70° C.; recovering at least a portion of said alumina ofsaid second aqueous slurry to thereby provide a recovered alumina; andforming an alumina support material comprising said recovered alumina bymixing said recovered alumina with water and a dilute acid to therebyform a paste having a pH in the range of from about 5 to about 9;forming a shaped particle of said paste; drying and heat treating saidshaped particle to thereby provide a heat treated shaped particle, whichcomprises at least 90 weight percent gamma alumina and less than 3weight percent silica, and wherein said heat treated shaped particle hasa single-modal pore volume distribution characteristic, pores having amedian pore diameter in the range of from 110Angstroms to 126 Angstroms,a pore size distribution width of less than 33 Angstroms, a pore volumethat is related to said pore size distribution width such that said porevolume (PV) is greater than or equal to a value as determined by 0.7+0.004 x (w) wherein (w) is said pore size distribution width inAngstroms of said heat treated shaped particle, wherein less than5percent of said pore volume is present in said pores having a porediameter of greater than about 210 Angstroms.
 12. A composition suitablefor use as a component of an alumina support material, said compositionconsists essentially of: alumina capable of providing for said aluminasupport material having a single-modal pore volume distributioncharacteristic and comprising pores having a median pore diameter in therange of from 112 Angstroms to 122 Angstroms, a pore size distributionwidth of less than 33 Angstroms, a pore volume that is related to saidpore size distribution width such that said pore volume (PV) is greaterthan or equal to the value as determined by 0.7 +0.004 x (w) wherein (w)is said pore size distribution width in Angstroms, wherein less than5percent of said pore volume is present in said pores having a porediameter of greater than about 210 Angstroms and wherein said aluminaincludes no more than a small concentration of silica.
 13. A compositionas recited in claim 12, wherein said small concentration of silica isless than 3 weight percent of said support material.
 14. A compositionas recited in claim 13, wherein said alumina is substantially entirelypseudo-boehmite.
 15. A composition as recited in claim 14, wherein saidalumina comprises at least 90 weight percent pseudo-boehmite.
 16. Acomposition as recited in claim 15, wherein said alumina is made by themethod comprising the steps of: forming a first aqueous slurry ofalumina by mixing, in a controlled fashion, a first aqueous alkalinesolution and a first aqueous solution of a first aluminum compound so asto thereby provide said first aqueous slurry having a first pH in therange of from about 9 to about 10 while maintaining a first aqueousslurry temperature in the range of from about 25 to 30 ° C.; thereafter,increasing said first aqueous slurry temperature to the range of fromabout 50 ° C. to 65° C. to provide a temperature adjusted first aqueousslurry; forming a second aqueous slurry, comprising said alumina, byadding in a controlled fashion to said temperature adjusted firstaqueous slurry a second aqueous solution of a second aluminum compoundand a second aqueous alkaline solution so as to thereby provide saidsecond aqueous slurry having a second pH in the range of from about 8.5to 9 while maintaining a second aqueous slurry temperature in the rangeof from about 50° C. to 65° C.; recovering at least a portion of saidalumina of said second aqueous slurry.